fix(ocr-pipeline): show sub-columns in reconstruction and LLM review steps

- Add marker/bbox_marker fields to WordEntry type
- Add page_ref/column_marker colors to StepReconstruction
- Make StepLlmReview table dynamic based on columns_used metadata,
  showing all detected columns (EN, DE, Example, page_ref, marker)
  instead of hardcoded EN/DE/Beispiel only

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

admin-lehrer/app/(admin)/ai/ocr-pipeline/types.ts

@@ -181,12 +181,14 @@ export interface WordEntry {
   german: string
   example: string
   source_page?: string
+  marker?: string
   confidence: number
   bbox: WordBbox
   bbox_en: WordBbox | null
   bbox_de: WordBbox | null
   bbox_ex: WordBbox | null
   bbox_ref?: WordBbox | null
+  bbox_marker?: WordBbox | null
   status?: 'pending' | 'confirmed' | 'edited' | 'skipped'
 }